1. Field of the Invention
There have been increasing efforts to develop convenient and sensitive techniques for determining either qualitatively or quantitatively a wide variety of compounds of interest, either physiological or non-physiological. Many of the compounds are haptenic, frequently drugs, and are monitored in the treatment of mammals. Other compounds are naturally occurring compounds which are used for the diagnosis of dysfunctions such as auto antibodies and surface antigens on neoplastic cells. Other assays are concerned with the presence of microorganisms, particularly as evidenced by a distinctive surface antigen.
Depending upon the nature of the analyte and its source, the nature of the assay can be affected. Where the analyte cannot be obtained in pure form, labeling of an impure mixture of the analyte can result in a substantial amount of background signal. For the most part, other than monoclonal antibodies, antiserum is a complex mixture of antibodies. Again, labeling of a heterogeneous antiserum can also result in a large background signal. Other considerations involve interference from materials naturally occurring in the sample, manipulative convenience, sensitivity to variations in concentration in the range of interest of the analyte, available instrumentation and the like.
As the need has increased for increasing sensitivity and dependability, new protocols employing new reagents have been sought. Each new improvement has been only difficultly achieved in the light of past experience. Means for amplifying the signal resulting from the presence of analyte has been one approach to provide greater sensitivity. Many of these assays have depended upon enzymes or fluorescers because of many advantages which they afford. with fluorescers, it is desirable to be able to modulate a large number of fluorescer molecules in relation to each molecule of analyte.
2. Description of the Prior Art
U.S. patent application Ser. No. 28,640, now U.S. Pat. No. 4,256,834, filed Apr. 9, 1979, discloses the use of charcoal as a scavenger particle in competitive protein binding assays. U.S. Pat. No. 3,853,987 describes fluorescent particles in a competitive protein binding assay. U.S. Pat. No. 3,900,558 describes the uptake of fluorescent molecules by mast cells in an assay. U.S. Pat. No. 4,061,466 describes the use of gel particles for entrapping reagents in assays. U.S. Pat. No. 4,102,990 describes the use of particles of different electrophoretic properties, which are bound together by specific binding complexes in an assay. U.S. Pat. No. 4,138,213 describes the use of rheumatoid factor and Clq for particle agglutination in an assay. Application Ser. No. 964,099 now U.S. Pat. No. 4,275,149, at page 68, teaches charcoal as a quencher inhibited from entering a fluorescein containing particle.